High-frequency apparatus



March 15, 1949. A. E. HARRISON HIGH-FREQUENCY APPARATUS Filed May 20,1944 m UE INVENTOR ARTHUR E. HARR [SON ATTORNEY was 2 m m S no PatentedMar. 15, 194.9

HIGH-FREQUENCY APPARATUS Arthur E. Harrison, Rockville Centre, N. Y.,as-

signor to The Sperry Corporation, a corporation of Delaware ApplicationMay 20, 1944, Serial No. 536,467

The present invention relates to the art including ultra high frequencyelectron discharge tubes, and is more particularly concerned with suchtubes wherein cavity resonators are used to vary the velocity of anelectron beam, and the electrons are thereafter bunched.

In prior U. S. Patent No. 2,281,935, issued May 5, 1942, to R. H. Varianand W. W. Hansen, and in U. S. Patent application Serial No. 416,170,filed October 23, 1941, in the names of W. W. Hansen, J. R. Woodyard, S.F. Varian and R. H. Varian, and now Patent No. 2,4 5,738, issued August19, 1947, there are disclosed vacuum tubes of the above type used asfrequency multipliers, in which an electron beam, velocity bunched bythe action of an input resonator tunedL to and excited at a firstfrequency, excites an output resonator tuned to a harmonic of theenergizing frequency and spaced a predetermined distance from the inputresonator.

It is an object of the present invention to provide an improved cavityresonator suitable for use in such frequency multiplier vacuum tubes,and having smooth and stable frequency characteristics.

It is a further object to provide an improved cavity resonator having aneffective fixed lumped capacitance and an effective variable tuningcapacitance.

Another object is to provide an improved electron discharge devicehaving a cavity resonator embodying an inner cylinder rigidly positionedwith respect to the outer shell of said resonator.

A further object is to provide an improved frequency multiplier orharmonic generator having an input resonator embodying an inner cylinderrigidly positioned with respect to the outer shell of said resonator.

Still a further object is to provide an improved velocity variationfrequency multiplier or harmonic generator having an input resonatorembodying an inner cylindrical conductor forming an electron drift tuberigidly positioned within an outer shell of said resonator.

Another object is to provide an improved input cavity resonator for avelocity variation frequency multiplier so constructed as to insure substantially coaxial relation between adjacent grids of said frequencymultiplier input resonator.

Other objects will become apparent from the specification, taken inconnection with the accompanying drawing, wherein the invention isembodied in concrete form.

In the drawing,

31 Claims. (Cl. 315-6) Fig. 1 is an elevation, partly in cross-section,of a velocity-variation electron discharge device adapted to be used asa frequency multiplier;

Fig. 2 is a view partly in cross-section, of an improvedvelocity-variation frequency multiplier embodying the principal featuresof the present invention;

Fig. 3 is an elevation, partly in cross-section, of a portion of avelocity-variation frequency multiplier similar to that shown in Fig. 2,showing an alternative arrangement for excitation of thevelocity-variation device of Fig. 2; and

Fig. 4 is an elevation, partly in cross-section, of a somewhat differentarrangement of elements in a velocity-variation frequency multiplierembodying the present invention.

Like reference numerals are used throughout the four figures to refer tothe similar portions thereof.

In Fig. 1 there is shown a velocity variation frequency multiplierembodying an input cavity resonator 6 of a type disclosed and claimed inpending application 416,170 referred to above. This input cavityresonator 6 comprises as its principal elements the cylindrical outershell 9, a rigid slightly conical end Wall 1, and an inner conductivecylinder 8 connected to outer shell 9 and movably supported therein bythe flexible diaphragm ll forming an end wall of the resonator oppositethe rigid end wall 7.

As will be explained in detail below, the velocity variation frequencymultiplier embodying input resonator 6 includes a cathode structure itpositioned adjacent end wall 1 of the input resonator, an output cavityresonator ll, means for adjusting the dimensions Within resonator 3 fortuning the input resonator to an excitation signal frequency, and meansfor tuning resonator ii to a harmonic of this frequency.

As discussed in more detail in the above-mentioned patent, the velocityvariation frequency multiplier is operated with the cathode electricallyheated for electron emission and supplied with high negative potentialwith respect to resonator 6. With a resonant source of ultra highfrequency energy coupled to resonator 6 through a coaxial line l5, l5and coupling loop M, a high-potential ultra high frequency electricfield is developed between end wall I and the end 27 of inner cylinder 8of resonator 6. Electrons are projected from cathode structure I3through a central circular opening in end wall 7 to be propelled alongthrough inner cylinder 8 into resonator ll, under the influence of tweenend wall I and end 21? of inner cylinder 8,

the electrons are velocity modulated by the ultra high frequency voltagefield produced in this region.

During the travel of the stream of electrons from this region along thedrift space bounded .f

by inner cylinder 8, the velocity modulation results in distribution ofthe electrons in spaced bunches. These bunches pass through an ultrahigh frequency, high voltage field region of the output resonator ii,and impart thereto high harmonic energy. This ultra high frequencyharmonic energy may be extracted from the out put resonator ll throughcoupling IE3 and applied to a suitable utilization device connectedthereto.

A pair of closely adjacent grids 29 and may be provided in the end 2'!of the innercylinder i3 and in the opening in rigid end wall l,respectively. Such a pair of grids, along with the closely adjacentmetal areas of rigid wall i and inner cylinder 8, serve as an effectivelumped or concentrated capacitance which, together with the distributedinductance and capacitance of input resonator (5, determines thefrequency of resonant response of the resonator.

In practice, it is often found that in order to allow resonator B to bebuilt as a compact unit, it is necessary to employ a large lumpedcapacitance at grids 29 and 3!), which normally could be provided onlyby decreasing the spacing between the grids to less than a reasonableminimum value. In order to increase the lumped capacitance at thispoint, while retaining ample spacing between grids 23 and 30, aconductive slightly conical flange 28 was attached to the end 27 of theinner cylinder 8, as described in the pending application referred toabove. The member 28 cooperates with rigid end wall 7 to provide additional capacitance, which acts in shunt with the capacitance betweengrids 29 and '30 to tune resonator 6 to a desired input frequency range.

The structure provided for tuning input resonator 6 comprises a flange23 rigidly attached to outer shell 9, and a second flange 2d rigidlyconnected to an extension it! of inner cylinder 8. A plurality of screws21, ill may be provided in suitably tapped holes through flange 23 forbearing against flange 24 to adjust the separation between the flanges.Although only two such screws are shown in the view of Fig. 1, there maybe three input resonator tuning screws employed in suitable threadedholes symmetrically located at 120 intervals through flange 23.

If the input tuning screws are provided with righthand threads,clockwise rotation of the screws is used to produce movement of innercylinder 8 axially away from rigid end wall l, to decrease thecapacitance therebetween and thus to tune resonator 6 to resonance at ahigher frequency.

A similar structure for tuning harmonic output resonator l1 comprises arigid metal plate 25 connected to the metal cylinder 53 extending withinresonator ii to form a movably supported part thereof. This plate, alsomay be provided with three tapped holes spaced at 120 intervals andaccommodating output tuning screws 22 which have rounded ends adapted tobear against the rigid flange 24.

Three springs 26 interspaced among output with the new frequency Wasachieved.

resonator tuning screws 22 and also among the input tuning screws may bestretched between flange 23 and end plate 25, through clearance holesprovided in flange 24. These springs provide axial tension formaintaining input tuning screws 2!, 2i and output screws 22 firmlyseated against the flange 24 which is common to the input and outputtuning structures.

In practical operation of the device shown in Fig. 1, a cathode heatingsupply and a high potential source are connected as described above, toprovide cathode electron emission and accelerating potential along theelectron path. A utilization device, such as a detector, is connected tooutput coaxial line it, and a source of ultra high frequency excitationenergy is coupled to the input resonator 6 through a coaxial line I5,US. may be of the order of 300 megacycles per second, for example.

The input resonator 6 is then tuned. by means of adjustment screws 2i,2! to the frequency of the excitation source coupled thereto, and theoutput resonator ll is tuned to the desired harmonic of the inputfrequency, e. g., the tenth harmonic, which in the above example wouldbe of the order of 3000 megacycles per second.

The device shown in Fig. 1 was found to be diiiicult to adjust forbestperformance; this was noted to be especially due to critical movementsof the input tuning screws, 2|, 2! required. for obtaining maximumharmonic output energy from resonator l'i. When a large change ofresonant frequency of the resonator 6 wasrequired to reach resonancewith acoupled source of excitation signal, it was necessary to makesmall successive adjustments on all of the input resonator tuning screwsin turn, repeating this procedure in a number of steps untilresonanceEven then, the resonator. 6 often was found to perform unsatisfactorilyunless minute adjustments of the different input tuning screws were madeto find the most effective combination of positions of all of the inputresonator adjusting screws.

After several successivev adjustments of .the input resonator tuningscrews, retracting one and advancing another, an adjustment of resonator6 eventually could be found at which very good performance was obtained.

The critical adjustment characteristics of input resonator 6 werebelieved to be largely due to the great axial extension of innercylinder 8 from an effective pivotal point in the vicinity. of flexiblediaphragm l l. Because of this, an advancement of a single inputresonator tuning screw, e. g., 2 l, while eifective as intended toproduce axial movement of inner cylinder 8 with respect to outer shell9, also resulted in a radial movement of the end 27 of inner cylinder 3which. was much greater than the resultant axial movement, Of course,only the axial movement was desired, since it was advantageous to retaingrids 29 and 30 in substantially coaxial positional agreement, so thatthe respective parts of the grids would remain aligned.

Moreover, the lumped loading capacitance provided by closely spacedelements 1 and 28 varied sharply when a relative radial movement betweenthese elements was produced by such differential adjustments of screws2| and 2i.

Of course, in the design of the frequency multiplier electron dischargedevice of Fig. 1, it was intended that large axial movements of element28 and grid 29 with respect toendwall' 1 The frequency of the excitationsource movements to negligibility.

and grid 30 for tuning over a large frequency range would beaccomplished with negligible radial motion of elements 28 and 29 withrespect to elements 1 and 30, by successive small adjustments of each ofthe input resonator tuning screws in turn. Actually, however, it wasfound difficult to so regulate the rotary adjustments of the tuningscrews as to restrict the above radial Furthermore, the alignment of theelements 8 and 28, and of elements 29 and 30 within the resonator 6could only be estimated on the basis of the performance of the frequencymultiplier tube, since these elements were hidden from view.

Then, too, while large changes of tuning of the input resonator wereaccomplished by small, successive movements of the difierent inputresonator screws in turn, the relatively small final tuning adjustmentsof the input resonator usually required concentration on a singleadjustment screw, as screw 2|, adjustment of which would result ingreater radial movement of elements 28 and 29 than axial movement ofthose elements, as explained above.

Thus, the structure shown in Fig. 1 of the drawing in this case, andshown and claimed in the above-mentioned application Serial No. 416,170,operated successfully after a tedious series of adjustments, butrequired great care in manipulation of the individual input resonatortuning screws to obtain best performance.

The present invention, in order to overcome the disadvantages aboverecited, provides in the frequency multiplier or harmonic generator ofFig. 2 an improved input cavity resonator characterized by substantiallyfixed alignment of the input resonator grids and the cathode, andfurther characterized by an inner cylinder 3 rigidly positioned withinshell 9. A further feature of this improved cavity resonator is theincorporation therein of a rigidly fixed capacitance loading element 33extending between the end 27 of the inner cylinder 8 and thecorresponding end of outer shell 9. This fixed capacitor is supplementedby an adjustable lumped capacitor comprising a metal cylinder 31 andelement 36 movable axially in closely spaced relation to the end 21 ofinner cylinder 8. Metal cylinder 31 and element 35 are separated axiallyfrom the end of inner cylinder 8 by a small annular gap which is variedby movement of element 36.

With these features the resonator 8' overcomes the critical adjustmentcharacteristics of the operation of the resonator 6 shown in Fig. 1.

In the form of resonator shown in Fig. 2, the rigid electricallyconductive cylinder 8 is rigidly connected to outer shell 9 throughrigid conductive end plate 32. Cylinder 3 and end plate 32, together,form a rigid conductive re-entrant member connected to outer shell 9 atone end thereof. Such a re-entrant member may be composed of a discportion and a cylindrical portion bonded together, or may be made as aunit by spinning or drawing a single piece of metal to the desired form.A large lumped loading capacitance is provided between the ends of outershell 9 and inner cylinder 8 by a conductive member 33 attached tocylinder 8 and extending between cylinder 8 and outer shell 9.Preferably, element 33 may include a disc portion 33' and a cylindricalportion 33", the latter having an outer diameter slightly smaller thanthe inner diameter of shell 9. Such portions, if desired, may be formedas a single metallic member spun from suitable sheet metal. Thecylindrical portion of element 33 provides a large capacitanceconcentrated between this element and the inner surface of thecylindrical shell 9.

Attached to the end of shell 9 adjacent capacitance element 33 is an endwall 34 provided with a flexible diaphragm 35 which permits movement ofadjustable flanged tuning element 38 relative to the end 2? of innercylinder 8 and also relative to the disc surface 33 of fixed capacitanceloading element 33. Flange 33 is connected through cylinder 31 to rigidflange 38, which in turn is attached through metal cylinder 39 and aglass extension 4| to a conventional vacuum tube base d2. Within themetal cylinder 39 is positioned a cathode structure I 3 similar to thatshown in Fig. 1. Also there is positioned within flange 38 anaccelerating grid 4'4 adapted to cooperate with cathode structure l3 inprojecting electrons axially along resonator 6' through the drift tubespace within conductive cylinder 8.

Adjustment screws 45 cooperating with suitably tapped holes throughflange 38, and compressed springs 56, provide means for adjustment ofthe spacing or gap between adjustable capacitor element 35 and the end21 of inner cylindrical conductor 8. Thus, while the large lumpedcapacitance provided by the closely spaced element 33 and shell 9 of thecavity resonator remains substantially constant by virtue of the rigidconstruction of these parts of th cavity resonator, tuning element 36may be variably positioned within the cavity resonator to provideresonant frequency adjustment throughout a predetermined small frequencyrange.

Th flanged tuning element 36 may be arranged to cooperate with the discsurface 33 of fixed loading capacitor element 33 as well as the end 27of inner cylinder 3, if a moderately wide range of input resonatortuning adjustment is desired. The flanged tuning element 33 not onlyprovides for a desired range of tuning adjustment, but also serves avery important additional purpose in the structure shown in Fig. 2, byelectrostatically shielding the disc surface 33' of fixed capacitorloading element 33 from flexible diaphragm 35. Even though the positionof the cylindrical member 31 is fixed with respect to shell 9 of thecavity resonator for a given adjustment of tuning screws 45 so that theouter and inner circular edges of diaphragm 35 are fixedly positioned,variations of atmospheric pressure due to barometric changes or toimpinging sound waves may cause movements or vibrations of the portionof flexible diaphragm 35 intermediate the inner and outer circularextremities thereof. Without the tuning flange 36 interposed betweenflexible diaphragm 35 and the disc face of the capacitance loadingelement 33, an appreciable variation of capacitance, and accordingly, anappreciable variation of resonator tuning would be caused by suchmovements of the flexible diaphragm.

By virtue of the unusual arrangement of parts in resonator 6', theflanged tuning element 36 is at substantially the same ultra highfrequency potential as diaphragm 35, so that small changes ofcapacitance between adjacent surfaces of these elements are ofnegligible effect on the resonant frequency of the resonator 6.

An output resonator ll comprising a cylindrical outer wall 5|, aflexible diaphragm 52 and an inner conductive cylinder 53 may befastened to rigid end wall 32, employing the outer surface 54 of thiswall of the input resonator as a conductive surface portion of cavityresonator I1.

Coaxial line l8-is sh'owrl'prcvided with a coupling loop 55 extendingwithin cavity resonator l? for extraction of ultra high frequency energytherefrom.

Tension springs 25 and adjustment screws 22 are provided in a disc orflange 25 rigidly connected to inner cylinder 53 of the outputresonator. These adjustment screws and springs permit the spacingbetween disc wall surface d and the inner cylinder 53 of the resonator Hto be adjusted as desired for tuning the resonator H to a desiredharmonic of the input resonator excitation signal. Grids fat and il maybe provided Within wall surface 55; and inner cylinder 53, respectively,if desired.

In the construction of an input resonator 6 as shown in Fig. 2, caremust be exercised to insure that the large capacity loading element 33is so dimensioned, relative to the dimensions of the inner cylinder 3and the outer cylindrical shell 9, as to tune the resonator 5 to afrequency slightly higher than the desired operating frequency. Thesmall variable capacitance added by the flanged capacitance element thenprovides adjustment of the tuning of resonator B to the precisefrequency desired.

In Fig. 2, a coupling loop ill and a coaxial line having an innerconductor l5 and an output conductor i6 is shown inserted at a point oflow potential and high current and magnetic field strength within theresonator 5. Such a coupling element is suitable for introduction of lowfrequency power into the resonator ii from a low impedance source. Ifdesired, however, a high 1'. .pedance input coupler may be provided inresonator 6' as shown in the partial view in Fig. 3, wherein is shown amodification of the structure of 2 to provide a conductive lead 52fixedly positioned in an opening through outer shell 9 by a glass seal53 and connected to a capacitance loading element 33 as by a solderedjoint 6- 5. An outer tubular conductor 65 connected to outer shell 9 asby a soldered joint may be provided along with lead to form therewith ahigh impe ance coaxial line for input connection to the resonator b. Ifan intermediate impedance coupier is desired the conductor 62 may beconnected to any point along inner cylinder it instead of capacitanceloading element Figure l shows a modification of the structure of Fig.2, in which the rigid relation of the cylindrical conductor 8 and theouter shell ii is retamed a the inner cylinder 8 encloses the oathodeassembly it on an insulated supporting structure 68. With thisarrangement, the direction of the electron stream projected from theoathode structure 53 through the grids 29 and 3d of resonator S issubstantially the opposite of that shown in Fig. 2, so that the electrondrift tube til may be made external of the resonator 6 and may be madeof any length shorter than resonator 5" if desired. This has theadvantage of permitting greater design flexibility of resonator ii,substantially independent of the drift tube length requirements of avelocity variation frequency multiplier tube structure.

In Fig. 4, conductive cylinder 29 supporting at one end the flangedtuning member 36' is rigidly fastened to adjustable flange "l, and isextended beyond this flange to provide the inner cylindrical conductorl2 of output resonator Ii. A rigid fiange 58 is provided on outputresonator l? for adjustment through screws 51 of the spacing betweenoutput resonator grids 59 and 6! for changing the lumped capacitancetherebetween *to' tune the resonator. For this purpose, screws againstflange ll.

*lange l l is also adjusted with respectto'end wall t l of input cavityresonator 6"by screws which are seated in threaded holes through flangeH and bear against wall 34' to permit relative adjustment of the spacingbetweenfiaiiged tuning element 36' and the disc portion of'the lumpedcapacitance loading element 33.

Otherwise than in the revision of the input resonator to permit thelocation of the cathode structure it within the boundaries of theresonator ii, and thus to permit a choice of drift tube lengthsubstantially independent of the length of resonator ii", the operationof the version of Fi 4 is substantially similar to that of thearrangement shown in Fig. 2, as will now'be described.

With the negative terminal of a source of high potential connected tocathode structure it '(or iii) and the positive terminal connected tothe metallic resonator structure E (or t") and with a source of filamentheater potential connected heat the cathode element within cathodestructure ill (or E3), source of ultra high frequency energy beconnected to the input coaxial line it, it or to the high impedancecoaxial line '32, E5, and input resonator t (or 6") easily may be tunedby adjustment of tuning screws 45 (or iii) to resonance with said ultrahigh frequency source. With an ultra high frequency utilization device,such as a detector, connected to output coaxial line it, tuning screws22 (or 5i) may adjusted to tune output resonator ll (or ll) for maximumoutput at a desired harmonic of the energy supplied to the inputresonator.

The improved non-critical performance of the input resonator embodyingthe present invention may then be observed by rotation of one of theinput resonator tuning screws 55 through a small angle in a clockwisedirection, and a similar rotation of another input tuning screw threadedin a similar sense through an equal angle in the opposite direction.With the first of these adjustments, it will be noted that the resonator5 is detuned from resonance with the source connected to coaxial lineI5, H5, resulting in a marked decrease of output from coaxial line it.With the second of these adjustments, the axial alignment of cathodestructure it andcylindrical structure 3? is shifted only very slightlywith respect to the axis of shell 8 and inner cylinder 8, and the tuningof resonator B is readily restored to resonance with the sourceconnected to coaxial line l5, It without any detectable relative radialdispl-..c merit between grids 29 and fill, and thus without appreciableimpairment of performance of the electron discharge device.

Thus, by the rigid positioning through end wall 32 of inner conductivecylinder 3 and capacitor loading element with respect to outer shell 9,and the very short axial length of the structure connecting flange 3a(or ill) and the adjustable flange (or $33) the radial movement offlange element at resulting from rotation of a tuning screwiii to obtaindesired axial movement of this element with respect to the end 21 ofinner cylindrical conductor i2 is greatly reduced. This results in high,mechanical and electrical stability of input resonator and permitsgreatly improved ease of timing adjustment of the input resonator. u I

Along with this improved. arrangement of elements in resonator 6', theradial extension of the flanged tuning element 35 is made sufficient toefiectively shield the flexible diaphragm 35 from the relatively highpotential surface of fixed capacitor element 33 and the end 21 of innercylinder 8, thus safeguarding against vibration and pressure-responsivemodulations of the energy supplied to input resonator 6.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. Cavity resonator apparatus comprising a conductive outer shell havina flexible wall at one end, a rigid conductive inner member fixed tosaid shell at the other end thereof and extending toward and adjacent tosaid flexible wall, conductive means supported at the central portion ofsaid flexible wall and opposite the end of said inner member anddefining a gap therebetween, for controlling the resonant frequency ofsaid resonator, and shielding means adjacent said flexible wall forpreventing vibration of said wall from modulating said resonantfrequency, said shielding means comprising a disc positioned adjacentsaid gap.

2. Cavity resonator apparatus comprising a conductive outer shell havinga flexible wall at one end, a rigid conductive inner member extendingfrom the other end of said outer shell toward said flexible wall,conductive means supported at said flexib e wall and opposite the end ofsaid inner member and defining a gap between said inner member and saidconductive means, and shielding means adiaccnt said flexible wall andextending radially a distance smaller than the inner diameter of saidshell and intermediate said flexible wall and said end of said innermember for preventing distortion of said wall from affecting theresonant frequency of said resonator.

3. Apparatus as in cTaim 2 further including means connected betweensaid conductive means and said shell for varying said gap whereby theresonant frequency of said resonator may be varied.

4. Cavity resonator apparatus comprising a conductive outer shell havinga flexible wall at one end, a rigid conductive inner member fixed tosaid shell at the other end thereof and extending toward and adjacent tosaid flexible wall, conductive means supported at the central portion ofsaid flexible wall and opposite the end of said inner member anddefining a gap therebetween, means connected between said latterconductive means and said shell for varying said gap to vary theresonant frequency of said resonator, and shielding means adjacent saidflexible wall for preventing distortion of said wall from affecting saidresonant frequency, said shielding means comprising a conductive discmember located adjacent said gap and connected to said flexible wall andbetween said flexible wall and said inner member.

5. An ultra-high frequency cavity resonator comprising a conductivecylindrical outer shell having a rigid conductive wall attached at oneend and a flexible conductive diaphragm attached at the opposite end, aconductive inner cylinder positioned within said outer shell and rigidlyconnected at one end to said rigid Wall and extending toward saidflexible diaphragm and providing lumped capacitance therewith, a fixedcapacity-loading element extending between said inner cylinder and saidouter shell and fixedly positioned with respect to said cylinder andsaid outer shell and means for varying said lump capacitance, comprisingmeans connected to said flexible diaphragm for axial adjustment thereoftoward said inner cylinder.

6. An ultra high frequency cavity resonator comprising a conductiveouter shell having a rigid conductive wall attached at one end and aflexible conductive diaphragm attached at the opposite end, a conductiveinner cylinder positioned within said outer shell and rigidly connectedto said rigid end wall and extending toward said flexible diaphragm, afixed capacitance loading element extending between said inner cylinderand said outer shell and fixedly positioned with respect to saidcylinder and said shell and providing a large capacitance therebetweenand a movable shielding flange connected to said diaphragm and extendingradially between said diaphragm and said conductive inner cylinderwhereby the direct capacitance between said flexible diaphragm and saidinner cylinder is rendered substantially ineffective.

7. Apparatus as in claim 6, wherein said fixed capacitance loadingelement comprises a conductive cylinder positioned adjacent the innersurface of said outer shell at said opposite end thereof and connectedto the end of said inner cylinder adjacent said diaphragm.

8. Ultra-high frequency electron discharge apparatus comprising aconductive cylindrical shell, a flexible conductive diaphragm connectedto said shell at one end and having an opening through the centralportion thereof, a rigid conductive disc connected to said shell at theother end, a conductive tube coaxially positioned within said shell andfixedly connected to said disc and also extending therefromsubstantially the length of said outer shell toward said flexiblediaphragm, a fixed capacitance loading element fixedly positionedcoaxially with said shell and said tube adjacent said flexible diaphragmthrough at least part of the radial spacing between said shell and tube,means including a cathode for projecting electrons through saidconductive tube substantially parallel with the axis of said shell, andmeans coupled between said diaphragm and said conductive tube forvarying the axial spacing between said flexible diaphragm and saidconductive tube for varying the tuning of said apparatus.

9. Ultra-high frequency electron discharge apparatus comprising aconductive cylindrical shell, a flexible conductive diaphragm connectedto said shell at one end and having an opening through the centralportion thereof, a rigid conductive end wall connected to said shell atthe other end, a first conductive tube coaxially positioned within saidshell and fixedly connected to said end wall and also extendingtherefrom substantially the length of said shell toward said flexiblediaphragm, a second conductive tube coaxially positioned within saidshell and connected to said diaphragm and extending therefrom towardsaid first conductive tube, a first conductive disc located adjacent oneend of said first conductive tube and extending radially to almostcontact said shell, said first disc having an axially extending flangepositioned at the periphery thereof parallel to and spaced from saidshell, 2. second conductive disc located adjacent one end of said secondconductive tube, said first and seca r-cease conductive discs forming avariable lumped c acitance, saidfiange portion of said first disc and:the adjacent portion. ofsaid shell formin a fixed lumped capacitance,means including a cathode for projecting electrons through saidconductive tubes Substantially parallel with the axis of said shell, andmeans for varying the axial spacing between said first and secondconductive tubes for varying the tuning of said apparatus.

10. Ultra high frequency apparatus comprising a resonator comprising aconductive outer shell having a rigid end wall and an opposite-end wall,a conductive cylinder fixedly positioned within said shell by aconnection to said rigid end wall-and extending axially within saidshell to ward'sald opposite wall-to substantially the axial extent ofsaid shell, a fixed capacitance loading element extending substantiallybetween said shell-and the end of saidiinner cylinder adjacent:

said opposite end wall, and an axial tuning ele ment supported in saidopposite end wall and movable for adjustment relative to the adjacentend of said inner cylinder whereby the tuning of said resonator may bevaried through a narrow frequency range.

11. Apparatus as in claim 10, wherein said tun ing element includes aradially extending conductivefiange between said opposite wall andsaidinner: cylinder for electrostatically shielding said opposite wallfrom said innercylinder.

12. Ultra highirequency electron discharge apparatus comprising aconductive outer shell having a rigid endwall and an opposite end wall',a

conductive cylinder fixedly positioned with respect tosaid shell byaconnection to said end wall= within said tuning eiement, a second gridposi tioned' in the end of saidinner cylinder adjacent said tuningelement, and means. including a source of electrons positioned coaxiallywith said inner cylinder and for projecting said electrons through saidgrids and said inner cylinder for oscillatory coupling therewith.

13.- In a velocity variation harmonic generator comprising an ultra highfrequency input resonator, an output resonator or positioned coaxiallywith said input resonator and adapted to be tuned to harmonic relationwith said input resonator means including, a cathode positioned adjacentsaid inputresonator for projecting electrons along an axial path throughsaid input resonator and said output resonator in turn, the input resonator comprising a conductive outer shell having a rigidendwall, aconductive cylinderfixedlypositioned within said shell'by a connectionto said end'wall andextending axially within saidshell to substantiallythe axial extent of said shell, a

fixed capacitance loading element extending be of said inner cylinderwherebythetuning of said 12 l; resonator may be varied through a narrowfrequency range.

14:. A velocity variation harmonic generator as in claim 13 wherein saidcathode is positioned adjacent tuning element for projecting electronsthrough said tuning element and said inner cylinder in turn whereby saidinner cylinder provides an electron drift space.

15. A velocity variation harmonic generator as in claim 14 whereincathode is positioned within said inner cylinder for projecting elecrons therefrom through said tuning element.

16. An ultra iiin frequency'cavity resonator corn; i conductive wailattached at one end and a flexible conductive diaphragm attachedat theopposite end, conductive inner cylinder positioned within said outerbell and rigidly connected one end to said. rigid "wall and extendingsubstantially of said shell toward said fiexible diaphragm to form aninner conductive surface of said resonator, and" means attached to saidflexible diaphragm and extending toward said inner cylinder a stream ofeiectrons therethrough; said cavity resonator comprising a conductiveouter shell having a flexible wall at one end, a rigid holiow conductive'innermember fixed to said shell at supported at thecentral portionofflexible wall and opposite the end of said inner member and defining aresonant-frequency-controlling gap therebetween for traversal by saidelectron stream,- and shielding means adjacent said flexiole wall forpreventing distortion of said wall from affecting said resonantfrequency.

18. Cavity resonator apparatus comprising a conductive outer shellhaving a flexible wall at one end, a rigid conductive inner member fixedto said shell at the other end thereof and extending towardan'd'adjacent to said flexible wall, conductive means supported at thecentral portion of said fiexible wall and opposite the end of said innermember and defining a gap therebetween, for controlling the resonantirequencyof said resonator and shielding means adjacent said flexiblewall for preventing distortion. oi said wall from affecting saidresonant frequency, shielding comprising a flanged member connected'tosaid flexible wall and between said flexible wall and said inner member.

19. An ultra high frequency cavity resonator comprising'a conductiveouter shell having a wall at one end, a conductive inner member rigidlyconnected to said shell at the other end thereof and extending towardsaid wall, a capacity-deading element extending between said innermember near an end'thereof and said shell and rigidly fixed with respectto said member and said shell, and a movable member connected to thecentral portion of said end wall and defining a variable gap with theinner end of said inner member.

20. Anultra high frequency cavity resonator sing a conductive outershell having a rigid ig effectively lumped. capacitance therewith, saidcapacitance means 1e other end thereof and extending toward and adjacentto said flexible wall, conductive means said comprising a conductiveouter shell having a first conductive Wall attached at one end and asecond conductive wall attached at the other end, an inner conductorcoupled to said first wall and ex-- tending toward said second Wall andproviding a lumped capacitance therewith, and a capacity loading memberconnected to said inner conductor and forming lumped capacitance withsaid second wall and said outer shell.

21. Apparatus as in claim 20 in which one of said lumped capacitances isvariable.

22. Apparatus as in claim 26 in which one of said lumped capacitances isfixed.

23. Electron discharge apparatus comprising an ultra high frequencycavity resonator means a cathode positioned adjacent to said i forprojecting a stream of electrons therethrough, and means for coupling asource of high frequency oscillations to said cavity resonator forvelocity modulating said stream of electrons; said cavity resonatorcomprising a conductive outer shell having a wall at one end, a hollowconductive inner member rigidly connected to said shell at the other endthereof and extending toward said end wall, a capacity-loading ele mentextending between said inner member near the end thereof and said shelland rigidly fixed with respect to said inner member and shell, and amovable member connected at the central portion of said end Wall anddefining a variable gap with the inner end of said inner member.

24. A high frequency cavity resonator comprising a rigid outer shell, aninner member connected to said rigid outer shell and extending axiallytherewithin, means extending between said inner member said outer shellfor providing fixed efiective lumped capacitance therebetween, andfurther means extending between said inner member and said outer shellfor providing variable eiiective lumped capacitance therebetween.

25. A resonator comprising a conductive outer hell, an inner conductorcoaxial with said outer shell and connected therewith, conductive meansconnected to said inner conductor for providing a fixed lumpedcapacitance between said outer shell and said inner conductor, andfurther means extending between said outer shell and said innerconductor for providing variable lumped capacitance therebetween.

26. An electron discharge device comprising a cathode an outputresonator, and an input resonator ing a pair of electron-permeable wallportions positioned intermediate said output resonator and cathode, andcomprising a pair of rigidly connected coaxial members having rigidlyfixed lumped capacitance and variable lumped capacitance therebetween.

27. A resonator device comprising a pair of rigidly connected coaxialmembers having distributed capacitance, fixed lumped capacitance andvariable lumped capacitance therebetween.

28. An ultra-high frequency cavity resonator comprising a conductiveouter shell having a first conductive wall attached at one end and asecond conductive wall connected to the other end, an inner conductorcoupled to said first wall and extending toward said second wall, and acapacity loading means connected to the inner conductor and extendingradially to almost contact the outer shell, 2. part of said capacityloading means forming lumped capacitance with the said outer shell, anda iurther part of said capacity loading means forming a variable lumpedcapacitance with said second wall.

29. Apparatus as in claim 28 in which means are provided for varyingwith a minimum of radial displacement the axial spacing between the endof inner conductor extending toward said second wall and said capacityloading means.

39. An ultra-high frequency cavity resonator comprising a conductiveouter shell having a rigid conductive wall attached at one end and aflexible conductive diaphragm attached at the opposite end, ccndt iveinner cylinder positioned within said outer shell and rigidly connectedat one end to said rigid wall and extending substantially the length ofsaid shell toward said flexible diaphragm to form an inner conductivesurface of said resonator, a movable conductive disc spaced from saidflexible diaphragm and adjacent the end of said inner cylinder adjacentsaid diaphragm, and a capacity loading means connected to said one endof said inner conductor and extending almost to the inner surface ofsaid outer shell, 9. part of said capacity loading means forming fixedlumped capacitance with said outer shell, and a part of said loadingmeans formin variable lumped capacitance with said disc.

31. Apparatus as in claim 39 wherein positioning means having asubstantial pivotal point are provided for regulating with a minimum ofradial movement the axial spatial separation of said disc and saidcapacity loading means, the axial distance from the end of said disc tosaid pivotal point being small, whereby said radial movement isminimized.

ARTHUR E HARRISON.

REFERENQES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS 2,408,355 Turner Sept. 24, 1946

